At present, the color gamut of the mainstream liquid crystal display devices, including the flat display devices, is only 72 percent more or less, and the color gamut of some liquid crystal display devices is even lower. In order to improve the color gamut of the display devices, the quantum dot backlight technology has been developed. The color gamut of the display devices can be improved to 100 percent by the quantum dot backlight technology, and thus the color performance ability of the display devices is greatly improved.
However, there are significant disadvantages in the two structures in the prior art in which the quantum dot backlight technology is frequently used. In one structure, a backlight module with a quantum dot glass tube is used. In the backlight module with this structure, a distance between a blue light source and a light guide plate is increased, and a size of a quantum dot strip is increased accordingly. Consequently, a coupling angle of the light guide plate to the light source is not enough, and thus an extraction efficiency of the light guide plate declines. In another structure, a backlight module with a quantum dot diaphragm is used. There are too many scatterings in the backlight module with this structure, and thus the light loss thereof is increased. Therefore, it is necessary to improve the traditional backlight module so as to increase the light-exiting efficiency thereof.